title: Higher Chlamydia trachomatis prevalence in ethnic minorities does not always reflect higher sexual risk behaviour.
abstract: BACKGROUND
  In affluent countries, the prevalence of Chlamydia trachomatis (CT) is often higher in certain ethnic minorities than in the majority population. In The Netherlands, we examined why CT prevalence is higher in Surinamese/Antilleans, the largest minority in the country.
  
  
  METHODS
  Heterosexuals were recruited for a cross-sectional survey from May through August 2010 at the sexually transmitted infections (STI) clinic in Amsterdam. Participants completed a questionnaire and were tested for STI. A causal directed acyclic graph was assumed to investigate whether the association between ethnicity and CT could be explained by differences in sexual risk behaviour and socio-economic status.
  
  
  RESULTS
  Subjects included 1044 with Dutch background and 335 with Surinamese/Antillean background. Median age for the combined population was 25 (IQR 22-30) years, and 55.4% was female. Sexual risk behaviour did not differ significantly between the two groups. CT was diagnosed in 17.9% of Surinamese/Antilleans and in 11.4% of Dutch. Surinamese/Antilleans were significantly more likely to have CT (OR 1.70; 95% CI 1.21-2.38). The association between ethnicity and CT remained statistically significant after adjusting for sexual risk behaviour, age, sex, and ethnic mixing (aOR 1.48; 95% CI 1.00-2.18), but not after adjusting for education and neighbourhood, markers of socio-economic status (aOR 1.08; 95% CI 0.71-1.64).
  
  
  CONCLUSIONS
  The difference in CT prevalence between the minority and majority groups was not explained by differences in sexual risk behaviour. The higher CT prevalence found among Surinamese/Antilleans appeared to reflect their lower educational level and neighbourhood, two markers of lower socio-economic status. We hypothesise that the effect results from lower health-seeking behaviour.
authors.affiliation: Cluster of Infectious Diseases, Public Health Service of Amsterdam, The Netherlands. amatser@ggd.amsterdam.nl
authors.forename: Amy
authors.initials: A
authors.lastname: Matser
authors.forename: Nancy
authors.initials: N
authors.lastname: Luu
authors.forename: Ronald
authors.initials: R
authors.lastname: Geskus
authors.forename: Titia
authors.initials: T
authors.lastname: Heijman
authors.forename: Marlies
authors.initials: M
authors.lastname: Heiligenberg
authors.forename: Maaike
authors.initials: M
authors.lastname: van Veen
authors.forename: Maarten
authors.initials: M
authors.lastname: Schim van der Loeff
mesh_terms: D000328:Adult; D002690:Chlamydia Infections / Q000453:epidemiology* / Q000208:ethnology / Q000382:microbiology; D002692:Chlamydia trachomatis; D005260:Female; D006801:Humans; D008297:Male; D009426:Netherlands / Q000453:epidemiology; D009427:Netherlands Antilles / Q000208:ethnology; D010342:Patient Acceptance of Health Care; D015995:Prevalence; D012309:Risk-Taking; D012725:Sexual Behavior; D012923:Social Class; D013532:Suriname / Q000208:ethnology; D014505:Urban Population; D055815:Young Adult